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Ok, let's explain how the ignition system on the SR20 works.
In accordance to have spark, you need the following :
Constant power to the ECU (Pin # : 46, 109)
Switched Power(ignition) to the ECU (Pin # : 38, 47)
Ground to the ECU (Pin # : 13, 39, 48, 107, 108, 116)
Ok, those are the basic to make the ECU “work”.
Then when you crank to engine, the CAS send a signal to the ECU that tell him : "Hey, dude, i'm now at TDC of cyl # 1! Give some fuel and spark Mofo'!"
So to give spark, the coils need : 12V+ Power(Pin #2), Ground(Pin #1), and a switched ground(Pin #3)(this is the one that "trigger" the coils and make the spark, via the ignitor). (Pinout I gave is directly on the coils connectors)
To complicate the thing a little bit, Nissan decided to use an ignitor chip, which is basically just 4 transistors in a nice box. Each coil is connected to a pin of the Ignitor which is named A, B, C, D. Coil # 4 is Pin A and coil # 1 is Pin D, I let you figure out the 2 others (lolz). On the other side of the ignitor, there is 5 pins(1, 2, 3, 4, 5). Each one of those is connected to the ECU except for pin 3 that is connected to Ground. Pin # 1 of the ignitor is connected to pin # 1 of the ECU, Pin # 2 of the ignitor is connected to pin # 2 of the ECU, Pin # 4 of the ignitor is connected to pin # 8 of the ECU, Pin # 5 of the ignitor is connected to pin # 9 of the ECU. Like I said earlier, pin # 3 is connected to chassis ground(pin 13 of the ECU)
Sooooooo…, each time the CAS tell to ECU which cylinder is at, the ECU ground the corresponding pin (either 1, 2, 8, 9). When a pin is grounded, it trigger the transistor in the ignitor, which trigger a coil, which create a spark! Easy right!?
So, knowing those basics… let’s do some diagnostics. What could create a no spark condition on all plugs? Either : no voltage at the ECU, no voltage at the coils, no ground to the ECU, no ground to the coils, no ground to pin # 3 of the ignitor or no CAS signal going to the ECU.
Phew! That's a lot of info there!
I hope that will help!
Frank
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